The aim of this study has been to determine whether high dose intensive combination chemotherapy of patients with diffuse histiocytic lymphomas, utilizing measures to prevent infections such as laminar air flow isolation units and prophylatic oral nonabsorbable antibiotics, will result in an improved remission rate and a prolonged survival. Three patients have been entered onto the study to date. Excellent tolerance to the high doses of chemotherapeutic agents employed, the stress of reverse isolation, and the administration of the oral antibiotics was observed in those patients. Two patients have completed induction and both achieved complete remission which continues (3 and 16 months). The third patient has shown marked regression of disease after 3 courses of chemotherapy.